The present invention is directed to a liquid jet printer having (i) a droplet formation section, such as a piezoelectric transducer, (ii) a droplet charging section, such as parallel metal plates, and (iii) a droplet deflection section, for directing the path of the droplet to the desired location on a substrate to be printed. In the case of continuous jet printing, a stream of individual droplets is produced, with some of the droplets impinging on the substrate in the desired pattern. The remaining droplets are intercepted by a collection device, such as a gutter, and are recycled to the droplet formation section, rather than printed on the substrate.
U.S. Pat. No. 7,438,396 B2 discloses a continuous ink jet printer having an array of nozzles for simultaneously printing across the width of a substrate, such as a textile fabric. The range of deflection of the droplets is such that adjacent nozzles can overlap, to print a seamless pattern on the substrate. The deflection plates are spaced apart and oppositely charged, for example at 1 to 5 kV, to produce an electrical field. The charge on the droplets and/or the strength of the electrical field created by the deflection plates can be varied, to create more or less deflection of the droplet. In one example, uncharged droplets are not deflected and collect in the gutter.
During operation of the printer, liquid droplets can accumulate on the surface of the deflection plates. The accumulation may be caused by splatters from the gutter, misdirected drops, or from rebound of ink off the surface of the substrate that is being printed. The accumulation can coalesce on the surface of the deflection plate reducing the effective gap to below the breakdown potential of air and cause arcing from one plate to the adjacent oppositely charged plate.